UVA 10763 Foreign Exchange

思路：

　　用两个整型数组a,b，分别存每个学生的原始位置和目标位置，然后排序，必须是一一对应才可以进行交换。

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstdlib>
#define max 500005
#define FIN freopen("input.txt","r",stdin)
#define FOUT     freopen("output.txt","w",stdout)
using namespace std;
int main()
{
    //FIN;
    //FOUT;
    int a[max], b[max];
    int n;
    while (scanf("%d", &n) && n != 0)
    {
        bool ok = true;
        int m = n, cnt = 0;
        for (int i = 0; i < n; i++)
        {
            scanf("%d%d", &a[i], &b[i]);
        }


        sort(a, a + n);
        sort(b, b + n);

        for (int i = 0; i < n; i++)
        {
            if (a[i] != b[i])
            {
                ok = false;
                break;
            }
        }
        if (ok)
            printf("YES\n");
        else
            printf("NO\n");
    }
    return 0;
}